1. Field of the Invention
The present invention relates to a mobile communication system, a maintenance terminal, an adjacent cell information optimizing method, a program, and a recording medium.
2. Description of Related Art
In 3G (Third Generation) mobile systems, it is necessary to perform a handover process to continue communication while a mobile communication terminal (UE: User Equipment) is moved. The handover process is a process of changing a communication connection base station to another base station, in order, in the course of movement. In the 3G mobile systems using W-CDMA (Wideband Code Division Multiple Access), a handover process during call connection is controlled by a radio resource control (RRC) message. The radio resource control message is transmitted and received between a mobile communication terminal (UE) and a radio network Controller (RNC).
In the handover process, peripheral cell information is registered in a data base for adjacent cell information on the radio network controller (RNC) side. The peripheral cell information is information based on cells within a communicable range of the base station connected to the mobile communication terminal (UE), and it is the information of peripheral cells that is a handover target. The peripheral cell information is transmitted at the time of adding cell information based on the movement of the mobile communication terminal (UE). In an actual handover process, the mobile communication terminal (UE) sequentially monitors the reception quality of radio signals received from the base station based on the transmitted peripheral cell information. When the reception quality of radio signals received from the base station in a cell of a movement destination exceeds a regulated threshold value in the course of movement, the mobile communication terminal (UE) transmits a request signal of connection to the cell to the radio network controller (RNC). Then, the mobile communication terminal (UE) is connected to the base station of the handover destination. The information of the peripheral cells, to which the signal is not transmitted from the radio network controller (RNC), are only transmitted as information of detected set cells from the mobile communication network (UE) to the radio network controller (RNC). In addition, when the reception quality of pilot radio signals transmitted from the base stations of the peripheral cells exceeds a regulated threshold value, the mobile communication terminal (UE) cannot perform the handover process. A technique regarding handover in a mobile communication system is disclosed in Patent Document 1 of Japanese Patent Application Laid-Open No. 2002-369236.
The adjacent cell information of each cell is registered in the data base of the radio network controller (RNC) as described above. The data base is manually registered by a network operator based on base station (cell) design information. The data base is frequently renewed by network expansion. In this case, the adjacent cell information of each cell is manually managed and renewed. For this reason, particularly, in a city or the like where peripheral cells are close together, when additional base station (Node B) bodies are installed or when additional radio frequency blocks are installed, omission of information with regard to handover destination may occur due to artificial mistakes such as cell information registration mistakes. In addition, trouble in a call connection process may occur at a cell edge (vicinity of the boundary between cells) based on the problems in the handover process.